1. Field of the Invention
The present invention relates to a stereophonic sound reproduction system, and particularly, to a stereophonic sound reproduction system for compensating a low frequency signal which is attenuated when removing a crosstalk (i.e., cross-signal interference), and a compensation method thereof.
2. Background of the Invention
In general, a stereophonic sound reproduction system purposes a reproduction of an original sound of sound a person wants to listen to around his ears. The stereophonic sound reproduction system can be implemented by use of equipment for controlling stereophonic sound such as a playback (e.g., an MPEG-1 audio layer 3 (MP3)) or a Compact Disk Player (CDP) and equipment for reproducing the stereophonic sound such as a headset or a speaker.
Here, as illustrated in FIG. 1, upon reproducing stereo using speakers SPL and SPR, a large space to reproduce sound is ensured, which causes a crosstalk which the stereophonic sound of the left speaker SPL and that of the right speaker SPR are listened by being mixed.
That is, the sound coming from the right speaker SPR should be transferred only to the person's right ear, but it is actually transferred to his left ear as well. Similarly, the sound coming from the left speaker SPL should be transferred only to his left ear, but it is actually transferred to his right ear as well. Accordingly, the crosstalk occurs such that the person listens to more distorted sound with his ears as compared to listening to sound through an headset.
In order to solve the occurrence of the crosstalk in the typical stereophonic sound reproduction system, a compensating filter disposed at a front portion of an input port of each speaker is used to implement a crosstalk canceller for removing the crosstalk. However, when the stereophonic sound reproduction system is implemented using the typical crosstalk canceller, the performance of the crosstalk canceller is problematically lowered at a low frequency band.
FIG. 2 illustrates a transfer function of a sound source which is reproduced in a stereophonic sound reproduction system equipped with a typical crosstalk canceller.
In particular, FIG. 2 illustrates a transfer function that a left sound source is got to both left and right ears when a stereophonic sound reproduction system equipped with a typical crosstalk canceller reproduces stereophonic sound with positioning left and right speakers by ±30° based upon a listener.
Here, a solid line denotes a transfer function that the left sound source is got to the listener's left ear, and a dotted line denotes a transfer function that the right sound is got to his right ear.
For an ideal crosstalk canceller, the solid line must be 0 dB because the sound source must be transferred as it is without distortion. The dotted line must be −∞dB because the sound source must not be transferred.
However, in the crosstalk canceller provided to the typical stereophonic sound reproduction system, as shown in FIG. 2, the solid line (i.e., the transfer function that the left sound source is transferred to the left ear) is −5 dB level at a low frequency band of about 50˜300 Hz and thus is close to the dotted line (i.e., the transfer function that the right sound source is transferred to the right ear).
Therefore, in the stereophonic sound reproduction system equipped with the typical crosstalk canceller, the typical crosstalk canceller may not remove the crosstalk well at the low frequency band to thereby attenuate a mono component signal which is positioned at the low frequency band.
The attenuation of the mono component signal may be solved by designing the compensating filter of the crosstalk canceller to have plural coefficients, which may cause an increase in the number of times for calculation.